The present invention relates to a semiconductor device and method of fabricating it and, more particularly, to structures of load devices using polycrystalline silicon, structures of semiconductor devices utilizing load devices using polycrystalline silicon, and methods of fabricating them.
Heretofore, the following steps have been employed in order to form load devices on a semiconductor substrate using polycrystalline silicon.
First, as shown in FIG. 9A, a silicon oxide film 21 that is an insulating film is formed on a silicon substrate 20 by well-known techniques, and then a polycrystalline silicon film 22 is formed by well-known techniques.
Then, as shown in FIG. 9B, the polycrystalline silicon film 22 is patterned and etched away.
Thereafter, as shown in FIG. 9C, those portions of the polycrystalline silicon film 22 which should be maintained at high resistance as load devices are coated with a well-known masking material 23 by well-known techniques. In order to obtain low-resistivity portions which act as conductive interconnections or whose resistance is so low that an Ohmic contact can be made with other conductive interconnections, an impurity is implanted by well-known techniques.
Subsequently, if the masking material 23 is removed as shown in FIG. 9D, a load device portion 22(a) of high resistivity and low-resistivity portions 22(b) are formed.
However, in the above-described prior art method, the load devices and the conductive interconnections directly connected with the load devices are all formed horizontally with respect to the semiconductor substrate and so each load device occupies a large area. Numerous manufacturing steps are needed to form the masking material film for increasing the device densities of semiconductor devices and for forming the low-resistivity portions directly connected with the load devices.
Accordingly, the present invention achieves the following objects:
(1) The area occupied by each load device is reduced to increase the device-packing densities of semiconductor devices. PA1 (2) The area occupied by each load device is reduced to increase the device-packing densities of semiconductor devices.
Also, load on manufacturing steps for load devices is reduced.